Propagation of television images



358-86. OR 292269998 l5R Dec. 31, 1940. K. scHLEsxNGER 2,226,998

PROPAGATION OF TELEVISION IMAGES Filed Oct. 8. 1935 31 Q) n V 110; lLLLuiw-is uu u;

Patented Dec. 31, 1940 UNITED STATES PATENT OFFICE Kurt Schlesinger, Berlin, Germany, assigner, by

mesne assignments, to Loewe Radio, Inc., a corporation of New York Application October 8, 1935, Serial No. 44,064 In Germany October 11, 1934 3 Claims.

In television receiving stations it is often required t0 ,d Ltrmuteateleyisal;,$inil-smlguo Qtllllglisiomreceirerhtohaaplralitrmf.subte... st aulyQriAsn, where usually cathode ray tubes are used. The distribution of the very weak current necessary for the heating and plate potential of these tubes, may be performed without difficulty by means known in the installation art. Diniculties arise, however, for the distribution of the ray deliecting and modulation control potentials. The relaxation potentials for deflecting the ray particularly at the line frequency, contain very high harmonics. For example, the fundamental line frequency in the case of a ZOO-line image amounts to 5,000 periods, and in a perfect sawtooth wave form the frequency of 60,000 cycles per second is still present to an appreciable extent.

A cable carrying the frequency accordingly radiates strongly. The screening of such cables would be accompanied by the difficulty that the capacity would be considerably increased, and in this way the load on the relaxation generator would become too heavy. An additional disadvantage in distributing such potentials by ordinary cables is the mutual coupling of both deflecting potentials. If the modulation control potential, which is considerably smaller than the deflecting potentials and oscillates, for example, with an amplitude up to the order of 10 volts, is also passed in the vicinity of the deflectingpotential lines, which are traversed by a severalhundred volt amplitude, there also occur strong interferences both in the modulation control and deecting potential.

The present invention relates to means for distributing image modulation currents and deflecting potentials of cathode ray tubes which avoid the above described interferences.

The present invention may be best understood by referring to the drawing, wherein:

Figure 1 shows a system including the features of the present invention, and

Figure 2 is a detailed showing of the cable used to connect the receiver and deflection voltage generators to the various cathode ray tubes.

In Figure 1, A represents a cathode ray tube located at the central receiving station, the tube including a glass envelope I3, deflecting plates I-| and 2,-2, anode I6, cathode I4 and Wehnelt cylinder or control electrode I5. For energizing the heater of the cathode, a source of potential I'I is provided, and the anode I6 is energized by the source of potential I8. A double push-pull relaxation generator for line (horizontal) and image (vertical) deflection is provided at 3| and 32, the energy from the deflection generator being connected as usual to the deiiecting plates I-I and 2 2. The detected and amplified picture or image signals are derived from the element I2 which represents a portion of the television receiver, and particularly the final video amplifier stages of the receiver. The output from the element I 2 is, of course, applied between the control electrode and the cathode of the cathode ray tube in order to modulate the beam produced thereby.

In order to transmit the deflection voltages as well as the picture signals to the subscriber stations or outlying television receiving tubes, a cable is used which is shown at 4 in both Figures 1 and 2. This cable has five conductors, four of which are placed about and equally spaced from a central or fth conductor.

The deection generators shown at 3| and 32 each produce, as stated above, deflection voltages which are push-pull in nature, a central point of each generator being connected to ground. Accordingly, as one plate of a pair is made positive, the cooperating plate of the same pair is made negative. The push-pull deflection voltage variations which are used for horizontally deflecting the cathode ray beam and which are applied to the deecting plates I-I', are also applied to the diametrically opposed conductors 5 and 5' of the inter-connecting cable. Likewise the pushpull voltage variations for causing vertical deflection of the cathode ray beam at image frequency are applied to the remaining diametrically opposed conductors 6 6 of the cable. The central conductor 1 is used to convey the picture or image signals from the received element I2 to the control electrodes of the various outlying television receiving tubes. In this way there is obtained an automatic decoupling of these lines in relation to each other, as each conductor is situated at that point at which the two conductors pertaining to the other circuit generate a zero potential.

Besides, by reason of this arrangement, which allows the conductors 5, 5' and 6, 6 to be located at a very small distance from the centre of the cable, the radiation of high frequency is avoided, as the conductor acts as bilar conductor.

Furthermore, it is possible in accordance with the invention to provide in the middle of this special cable a fth conductor 1, which is traversed by the image potential. The effect on this fifth conductor of the conductors 5, 5' and 6, 6 is in turn also balanced out in relation to both relaxation potentials owing to their push-pull operation. A screening or shielding of the entire bundle is, therefore, unnecessary in the majority of cases, so long as the spatial disposition of interfering apparatus is large as compared with the relative spacing of the conductors in the cable.

A screening or shielding means 8, when necessary, is placed surrounding the cable with the largest possible diameter, and passed to earth. Such screening may also be applied at single points.

The specic construction of the cable is best shown in Figure 2, wherein the central conductor 1 is shown, around which are positioned the four conductors for transmitting the deection voltages from the generators to the various subscriber stations.

The central conductor preferably contains resistances 9, which are grouped at various points along the conductor or which may be in the form of a distributed resistance and preferably a condenser I0 is connected in parallel with such resistance in order that the wide frequency range which is to be transmitted by the conductor 1 may be transmitted without selective frequency attenuation. Preferably also, at the end of the conductor 1, is connected a resistance Il to ground, in order to prevent reilection or absorption of various frequencies.

According to the invention, the deection plates I-l' are Yconnected to the opposite conductors 5 5 and the plates 2 2 to the opposite conductors 6--6', as stated above. If the cable contains only the five conductors,v then the conductors which carry the deflecting voltages may be placed at the corners of a square. As shown in Figure 1, the conductors of cable 4 connect the central or master tube A to the secondary or subscriber tubes B, one of which is shown in Figure l. 'I'he same may also be employed in multiple arrangement in the train of the same conductor.

The time constant R. C. produced by the R. C. member is a measure for the extent of the loading. 'Ihe same is all the smaller the better the conductor per se. As an example the members may have the values R equals 2000 ohms and C equals 100 mmf. for dimensioning and loading.

I claim:

1. A television receiving system comprising a central receiver and a plurality of remotely located image producing cathode ray tubes, each of said image producing tubes including means for generating a beam of electrons, a control electrode for modulating the beam of electrons and beam deflecting means adapted to be energized for causing bilateral deflection of the beam of electrons over a target area, means at the central receiver for supplying detected and amplified image signals and means for producing two series of push-pull voltage variations for energizing the beam deilectingmeans at each image producing tube, a transmission cable for connecting the central receiver to the image producing tubes including a plurality of pairs of conductors, the conductors of each pair being positioned on opposite sides of and spaced substantially equidistant from a common central conductor, means for connecting the means for producing each series of push-pull voltage variations to a pair of the conductors, and means for applying said image signals to the common central conductor for transmission to the beam deflecting means and the Control electrode, respectively, of the image producing tubes, whereby electrical coupling between the central conductor carrying the image signals and the pairs of conductors carrying the push-pull beam deflecting voltage variations will be substantially eliminated.

2. A television system comprising a central station and a plurality of remotely located image producing cathode ray tubes, each of said image producing tubes including means for generating a beam of electrons, a control electrode for modulating the beam of electrons and beam deflecting means adapted to be energized for causing deflection of the beam of electrons to scan a target area, means at the central station for supplying image signals and means for producing two series of push-pull voltage variations for energizing the beam deflecting means at each image producing tube, a transmission cable for connecting the central station to the image producing tubes including a plurality of pairs of conductors and a single conductor, the conductors of each pair being positioned on opposite sides of and spaced substantially equidistant from the single conductor, means for applying each series of push-pull voltage variations to a pair of the conductors, and means for applying said image signals to the single centrally positioned conductor for transmission to the beam deflecting means and the control electrode, respectively, of the image producing tubes, whereby electrical coupling between the single conductor carrying the image signals and the pairs of conductors carrying the push-pull beam deflecting voltage variations will be reduced to a minimum to substantially prevent the transfer of energy of the fundamental and harmonics of the frequencies present in the pairs of conductors from said conductors to the single conductor.

3. A television receiving system comprising a central receiver and a plurality of remotely located picture producing cathode ray tubes, each of said picture producing tubes including means for generating a beam of electrons, a control electrode for modulating the beam of electrons and beam deflecting means adapted to be energized for causing deflection of the beam of electrons to scan a target area, means at the central receiver for supplying picture signals and means for producing two series of push-pull voltage variations of different frequencies for energizing the beam deflecting means at each picture producing tube, a transmission cable for connecting the central receiver to the picture producing tubes including a plurality of pairs of conductors, the conductors of each pair being positioned on opposite sides of and spaced substantially equidistant from a common central conductor, means for applying each series of push-pull voltage variations to a pair of the conductors, and means for applying said picture signals to the common central conductor for transmission to the beam deflecting means and the control electrode, respectively, of the remotely located picture producing tubes, whereby the transfer of energy of fundamental and harmonic frequencies of the push-pull beam deflecting voltage variations from the pairs of conductors to the central conductor carrying the picture signals will be substantially eliminated.

KURT SCI-ILESINGER. 

